Extend the life of Guardair cartridge filters with Cloth Pre-Filter Bag. Cotton flannel bag installs over Standard, HEPA, and ULPA cartridge filters providing extra stage of filtration. Prevents wear and tear by capturing larger particles before they reach the cartridge filter. Washable and reusable. Replacement part for HEPA and ULPA filters. Upgrade part for Standard filter. For use with all 55, 30 and 20 Gallon Guardair Drum Vacuums and Vacuum Generating Heads.